1. Field of the Invention
The present invention relates to a control and mechanism for selectively positioning and locking the auxiliary transmission section of a compound transmission in a neutral position. In particular, the present invention relates to a control mechanism for the auxiliary section of a compound transmission of the type comprising at least one auxiliary section countershaft driven by the main transmission section and an auxiliary section output shaft selectively engageable by a shift mechanism with the auxiliary section countershaft and/or auxiliary section input wherein the control mechanism will selectively position and lock the shift mechanism to a neutral position preventing the application of torque from the auxiliary countershaft or input to the auxiliary section output shaft.
2. Description of the Prior Art
Compound change gear transmissions of the type comprising a main transmission section in series with an auxiliary transmission section, usually for vehicles, are well known in the prior art. The auxiliary transmission sections, of both the range and splitter type, usually comprised at least one auxiliary countershaft driven by the main transmission section and an auxiliary output shaft or mainshaft which was selectively clutchable to the auxiliary countershafts and/or directly to the auxiliary input. Often the main transmission section was directly shifted (as by a shift bar linkage assembly) or shifted through air or hydraulic valving, while the auxiliary transmission section was shifted by a master-slave valve control. Examples of such transmissions and controls can be seen by reference to U.S. Pat. Nos. 3,171,300; 3,283,613; 3,648,546; 3,799,002 and 4,192,196, all assigned to the assignee of this invention and all hereby incorporated by reference.
In the past, it has been known that the auxiliary countershafts can be utilized to drive added devices independently of the auxiliary output shaft, i.e. with the vehicle stationary, as through an auxiliary countershaft power take-off ("PTO") or the like. If the added device is to be driven while the vehicle is at rest, the main transmission section must be engaged to supply power to the auxiliary countershaft while the auxiliary mainshaft, or output shaft, must be disengaged, i.e. the auxiliary section must be in neutral.
As the main transmission must be engaged when the PTO was utilized, certain of the prior devices utilized controls to assure that when a power take-off was utilized with a stationary vehicle, the output shaft of the transmission could not be accidently engaged causing the vehicle to become unintentionally mobilized. These prior art controls were not totally satisfactory as they tended to be complicated, difficult to operate, excessively expensive, became inoperative in the event of a failure of the pressurized fluid supply and/or did not provide a positive positioning and locking function for the auxiliary transmission.